exercises

20. ubiquitous computing and augmented realities

EXERCISE 20.9 [extra - not in book]

A computer games manufacturer is producing a new game called Gulliver.  In this game the players travel through a virtual landscape in which are found various villages.  Some of these villages are occupied by Lilliputians, who are only 6 inches tall; some by ordinary people; and some by Brobdingnagians, who are giants.  The game uses a fully immersive VR headset.  You have been asked to advise the game makers.

  1. If the user ‘stands still’ in the virtual environment, a Lilliputian village that is very close, a normal village some way off and a Brobdingnagian village in the far distance will all look the same apparent size.  What visual cues can the designers use to enable a user to distinguish them?  (Say in your answer if any cues are better at distinguishing the miniature village from the normal one, or the normal one from the giant one.)
  2. How does this change when the user is allowed to move in the environment?
  3. The same manufacturer also produces 3D visualisation software for shopping market analysis.  A particular product lays out spheres in a 3D area where each sphere represents a shopper, the x,y,z coordinates represent age, income and length of stay in the shop and the size of the sphere represents the amount spent.  The resulting pictures are printed in colour, but users report difficulty in seeing the 3D nature of the diagram

    Briefly explain (referring to answers of parts (i) and (ii) where appropriate) why viewing the spheres in 3D is difficult and why an interactive 3D display could help.

answer available for tutors only

  1. N.B. There shuld be a careful distinction to be made between these answers and those of part (ii)
    • NO semantic cues
    • Stereo vision – better for miniature vs. bigger distinctions, but not so good for distinguishing normal from giant because of reduced angular distinction with distance.
    • Blue hazing with distance (especially good for normal vs. giant)
    • Occlusion effects – e.g. large person behind village would mean either person is giant and village is normal or person is normal and village is giant
    • Some possibility of perspective effects if the landscape includes strong linear features
  2. (ii)   Good students will notice that assumptions have to be made about the users’ size and rate of movement in the virtual world.
    • Various parallax effects due to sideways movement to give comparative distance between different villages
    • Rate of approach as one moves towards villages
    • Height of head – looking down on miniature village
    • Comparative size of user’s own virtual hand and body (where present) as the villages are approached
  3. The critical issues will have already been discussed above – this is reapplying them in a different context.

    Difficult because shapes are abstract and different sized spheres, mean size cannot be used as an indication of distance.

    Interactive 3D display allows effects like movement parallax etc., as in part (ii)

Other exercises in this chapter

ex.20.1 (tut), ex.20.2 (ans), ex.20.3 (ans), ex.20.4 (tut), ex.20.5 (tut), ex.20.6 (tut), ex.20.7 (open), ex.20.8 (tut), ex.20.9 (tut), ex.20.10 (tut)

all exercises for this chapter